ASChemistryCambridge (CIE)Exam Questions2. Atoms, Molecules & StoichiometryRelative Masses of Atoms & Molecules

Relative Masses of Atoms & Molecules (Cambridge (CIE) AS Chemistry): Exam Questions

Exam code: 9701

46 mins15 questions

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Relative Masses of Atoms & Molecules

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1
1 mark

Which expression defines the unified atomic mass unit?

  • the mass of an electron

  • \frac{1}{12} of the mass of an atom of carbon-12

  • the mass of an atom of hydrogen-1

  • the mass of a proton

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2
1 mark

What is the relative formula mass of ammonium sulfate, (NH4)2SO4?

  • 114.0

  • 114.1

  • 132.0

  • 132.1

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3
1 mark

Iron has many different naturally occurring isotopes.

Isotope

% Abundance

Isotopic mass

54Fe

5.845

53.9396

56Fe

91.754

55.9349

57Fe

2.119

56.9354

58Fe

0.282

57.9333

Using the information given, what is the relative atomic mass of iron?

  • 55.800

  • 55.845

  • 56.186

  • 56.250

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1
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1 mark

A sample of neon contains only the isotopes 20Ne and 21Ne.

The relative atomic mass of this sample is 20.2.

What is the percentage of 21Ne atoms in this sample?

  • 8%

  • 20%

  • 80%

  • 92%

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2
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1 mark

A sample of metal Z was analysed by mass spectrometry. The relative abundance of each isotope in a mass spectrum of the sample is shown.

m / z value

70

72

74

Relative abundance (%)

24.4

32.4

43.2

What is the relative atomic mass of metal Z to 3 significant figures?

  • 72.0

  • 72.2

  • 72.38

  • 72.4

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3
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1 mark

Hydrated copper(II) sulfate has the formula CuSO4·xH2O and a relative formula mass of 231.6.

What is the value of x?

  • 2

  • 3

  • 4

  • 5

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1
1 mark

An element consists of two isotopes 69X and 71X, whose abundances are 60% and 40% respectively. What is the relative atomic mass of element X?

  • 69.2

  • 69.8

  • 70.0

  • 70.2

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2
1 mark

A sample of strontium was analysed by mass spectrometry. The relative abundances of some of the isotopes are shown.

m / z value

84

86

87

88

% abundance

0.56

82.58

The relative atomic mass of this sample of strontium is 87.71.

Which row gives the percentage abundances of 86Sr and 87Sr?

86Sr

87Sr

A

6.96

9.90

B

8.43

8.43

C

9.90

6.96

D

11.58

5.84

    Choose your answer

    3
    1 mark

    Aspirin is a common analgesic used for the relief of aches and pains.

    Skeletal formula of aspirin showing a benzene ring with an ester group (OCOCH3) and a carboxylic acid group (COOH)

    Which row correctly describes aspirin?

    Empirical formula

    Molecular formula

    Mr

    A

    C2H2O

    C9H8O4

    180.0

    B

    C3H3O

    C9H12O4

    184.0

    C

    C9H12O4

    C9H12O4

    184.0

    D

    C9H8O4

    C9H8O4

    180.0

      Choose your answer

      4
      1 mark

      An element, X, has a relative atomic mass of Ar and exists as a diatomic molecule, X2.

      Which expression represents the total number of atoms present in m grams of the gas?

      (Where L represents the Avogadro constant.)

      • fraction numerator m L over denominator A subscript r end fraction

      • fraction numerator m L over denominator 2 A subscript r end fraction

      • fraction numerator 2 m L over denominator A subscript r end fraction

      • fraction numerator m A subscript r over denominator L end fraction

      Choose your answer